UN observers have inspected the site of an explosion which flattened a block of houses in the central Syrian city of Hama and killed at least 16 people, while the government and the opposition blamed each other for the blast.
Syrian state-run media said rebel bomb-makers accidentally set off the explosives. Anti-regime activists said intense shelling by government forces caused the extensive damage.
It was impossible to independently verify the conflicting accounts because President Bashar Assad's regime, facing a 13-month-old uprising, has restricted access for journalists and other outside witnesses.
Ahmad Fawzi, spokesman for UN special envoy Kofi Annan, said observers visited the site but he had no immediate word on what they saw.
Two UN observers are stationed in Hama, part of an advance team of 15 monitors who are visiting hot spots to try to salvage a ceasefire which is part of a peace plan aimed at ending the violence and bringing the two sides to the negotiating table. The observer team is to be expanded in the coming weeks to up to 300.
Amateur videos said to be of Wednesday's blasts in Hama showed a large cloud of white and yellow smoke rising from an area surrounded by green fields. In a later video, dozens of people searched through the debris, including huge chunks of cement and broken cinderblocks. Another clip showed the bloodied body of a little girl being carried through a crowd of wailing men.
The state-run Syrian news agency Sana said rebels mishandling explosives triggered the blast which killed at least 16 people and severely damaged at least six houses.
The Local Co-ordination Committees, a network of activists, denied that and said it was intense shelling from government tanks that caused the damage. The group put the death toll as high as 70, but that estimate was not confirmed by others.
Another opposition group, the Britain-based Syrian Observatory for Human Rights, said the cause of the destruction was not immediately clear. The Observatory initially cited reports by local residents that they had come under attack from regime forces.
However, the head of the group, Rami Abdul-Rahman, said he could not confirm those reports and called for an investigation by UN observers. He confirmed at least 16 people were killed.